U.S. patent number 4,564,768 [Application Number 06/489,089] was granted by the patent office on 1986-01-14 for contactless relay.
This patent grant is currently assigned to Fanuc Ltd.. Invention is credited to Michiya Inoue, Hidetsugu Komiya.
United States Patent |
4,564,768 |
Komiya , et al. |
January 14, 1986 |
**Please see images for:
( Certificate of Correction ) ** |
Contactless relay
Abstract
A contactless relay wherein the application of an A.C. signal to
the primary winding of a transformer is controlled by a command
input, and the A.C. signal obtained from the secondary winding of
the transformer is rectified into a D.C. signal by a rectifier
circuit. The D.C. signal drives a transistor switching element for
switching action. The switching element includes a single bipolar
transistor, or a pair of bipolar transistors which can be connected
in parallel to increase the current-carrying capacity of the relay.
The output terminals of the relay can be rendered non-polar by
constructing the relay of two bipolar transistors having commonly
connected emitters and commonly connected bases.
Inventors: |
Komiya; Hidetsugu (Hino,
JP), Inoue; Michiya (Hino, JP) |
Assignee: |
Fanuc Ltd. (Minamitsuru,
JP)
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Family
ID: |
13179225 |
Appl.
No.: |
06/489,089 |
Filed: |
April 27, 1983 |
Foreign Application Priority Data
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Apr 27, 1982 [JP] |
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57-61716[U] |
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Current U.S.
Class: |
307/140;
327/482 |
Current CPC
Class: |
H03K
17/601 (20130101) |
Current International
Class: |
H03K
17/60 (20060101); H03K 017/56 () |
Field of
Search: |
;307/125,127,130,132E,140,240,244,571,575,577,583,584
;363/18-21,131-134 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2132572 |
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Jan 1972 |
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DE |
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2533107 |
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Oct 1977 |
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DE |
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2850841 |
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Aug 1979 |
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DE |
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3028986 |
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Mar 1982 |
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DE |
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3125242 |
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Mar 1982 |
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DE |
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Other References
Electronics, vol. 43, No. 14, Jul. 6, 1970, p. 78, New York, U.S.,
C. H. Ristad, "Switched Oscillator Controls Four-Wire Resistance
Checks". .
Electronics Design, No. 7, Apr. 1, 1970, p. 77, Rochelle Park,
U.S., C. A. Herbst "Solid-State Isolation Relay has Nonpolarized
Terminals". .
Solid-State Relay by Evans et al., "Electronic", vol. 51, No. 13,
Jun. 22, 1978, p. 108..
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Primary Examiner: Scott; J. R.
Assistant Examiner: Jennings; Derek S.
Attorney, Agent or Firm: Staas & Halsey
Claims
What we claim is:
1. A contactless relay comprising:
oscillating means for generating an A.C. signal;
a transformer having primary and secondary windings for delivering
the A.C. signal from said oscillating means, the A.C. signal being
applied to the primary windings and delivered from the secondary
windings;
AND gate means having a first input operatively connected to
receive said A.C. signal, a second input operatively connected to
receive input and an output, for providing said A.C. signal in
accordance with said first and second inputs;
a transistor having a base operatively connected to said output of
said AND gate means, a collector operatively connected to said
primary of said transformer, and an emitter for applying said A.C.
signal to the primary windings of said transformer;
a diode having an anode operatively connected to a first end of
said secondary of said transformer and a cathode, for rectifying
the A.C. signal obtained from the secondary windings of said
transformer, said diode producing a rectified output;
a smoothing circuit including a capacitor operatively connected to
said cathode and to a second end of said secondary, and a resistor
having a first end operatively connected to said cathode and a
second end, for smoothing the rectified output produced by said
diode and for delivering a D.C. output signal; and
bipolar transistor switching means driven by the D.C. signal from
said smoothing circuit and including --
a pair of bipolar transistors having interconnected emitters,
interconnected bases operatively connected to said second end of
said resistor and respective collectors,
a pair of diodes respectively and backwardly connected across a
corresponding emitter and collector of one of said pair of bipolar
transistors.
2. A contactless relay according to claim 1, wherein said
collectors are interconnected to form an output and said
interconnected emitters form another output.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application is related to copending application U.S. Ser. No.
474,337.
BACKGROUND OF THE INVENTION
This invention relates to a contactless relay which relies upon
electronic circuitry to perform the same function as a relay with
contacts.
A relay having mechanical contacts, such as a reed relay, is
employed widely in the art for transmitting signals between two
systems having different signal levels, as when interfacing a
numerical control device and machine tool. The relay with contacts
applied in this fashion is ideal in that its output terminals are
non-polarized, its input and output are isolated DC-wise, and it is
small in size. Nevertheless, relays with contacts of a mechanical
nature are disadvantageous in that they have a shorter lifetime
than contactless relays owing to contact wear, and in that they
also exhibit lower operating speed. In response to the need for
further development of a relay without contacts, many contactless
relays incorporating different kinds of electronic circuitry have
been proposed, but none have the aforementioned excellent
properties possessed by relays provided with contacts.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a
contactless relay of small size and long life or "semipermanent"
nature, the input and output whereof can be isolated DC-wise.
Another object of the present invention is to provide a contactless
relay of small size and long life or "semipermanent" nature, the
input and output whereof can be isolated DC-wise, and having output
terminals which are non-polarized, similar to the non-polarized
output terminals of a relay with contacts.
Still another object of the present invention is to provide a
non-polarized, contactless relay having an extremely high switching
speed.
According to the present invention, the foregoing objects are
attained by providing a contactless relay having a transformer the
primary and secondary windings whereof pass an A.C. signal from an
oscillator circuit which produces the A.C. signal, the application
of the A.C. signal to the primary winding from the oscillator
circuit being controlled by a command input signal. The A.C. signal
from the secondary winding is rectified by a rectifier circuit and
then smoothed by a smoothing circuit to produce a D.C. signal which
drives a bipolar transistorized switching element. In an embodiment
of the invention, the switching element comprises a pair of bipolar
transistors having commonly connected emitters and commonly
connected bases, with a diode being backwardly connected across the
emitter and collector of each transistor. A load is connected
across the collectors of the transistor pair, the collectors
serving as non-polarized output terminals owing to the particular
connection of the transistors. In another aspect of the invention,
the switching element consists of a single bipolar transistor the
emitter and collector whereof serve as output terminals connected
to a load. Plural bipolar transistors can be connected in
parallel.
Other features and advantages of the present invention will be
apparent from the following description taken in conjunction with
the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram illustrating an embodiment of a
contactless relay according to the present invention;
FIG. 2 is a circuit diagram illustrating another embodiment of a
switching element shown in FIG. 1; and
FIG. 3 is still another embodiment of the switching element shown
in FIG. 1 .
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference will now be had to FIG. 1 to describe an embodiment of a
contactless relay in accordance with the present invention. The
relay comprises an oscillator circuit 1, specifically a pulse
oscillator circuit such as an astable multivibrator, and a
transformer drive circuit 2 having an AND gate AND and a transistor
TR. The AND gate AND, which receives the output of the oscillator
circuit 1 at one input terminal thereof, is gated open when a
command input terminal IN connected to the other input terminal
thereof goes high (logical "1"), whereby the AND gate delivers the
oscillator circuit output to the base of the transistor TR. The
relay further comprises a transformer 3 having its primary winding
connected to the collector of the transistor TR in the transformer
drive circuit 2. Thus the transformer 3 is driven by the transistor
TR turned on and off by the output of the oscillator circuit 1. The
secondary winding of the transformer T is connected to a rectifying
circuit 4 having a diode D for rectifying the A.C. power developed
by the secondary winding of the transformer. A smoothing circuit 5,
comprising a capacitor C and a resistor R connected in series, is
operable to smooth the output of the rectifying circuit 4 to
provide a D.C. signal. The relay of the present invention also
includes a switching element 6. According to a preferred
embodiment, the switching element 6 comprises a pair of rapid
switching, bipolar transistors 6a, 6b. The emitters of the
transistors 6a, 6b are tied together and connected to one output
terminal of the smoothing circuit 5, and the bases thereof are
similarly tied together and connected to the other output terminal
of the smoothing circuit 5. The collectors of the respective
transistors 6a, 6b constitute output terminals out.sub.1, out.sub.2
for connection to a load. The switching element 6 also includes
diodes 6c, 6d, connected backwardly across the collector and
emitter of the transistors 6a, 6b, respectively, in order to
prevent the application of a reverse bias voltage.
In the operation of the relay shown in FIG. 1, a high-level signal
is applied to the command input terminal IN from externally located
control means (not shown) to turn on, i.e., close, the relay. The
high-level signal opens the AND gate AND of the drive circuit 2,
applying the oscillatory output of the oscillator circuit 1 to the
base of transistor TR. The latter is switched on and off by the
oscillatory signal at its base and drives the primary winding of
the transformer 3 connected to its collector, whereby a voltage is
induced in the secondary winding of the transformer. A.C. power
thus is obtained from the secondary winding and is subsequently
rectified by the rectifying circuit 4 and smoothed by the smoothing
circuit 5, providing a direct current. The D.C. output of the
smoothing circuit 5 is applied to the bases of the transistors 6a,
6b, thereby driving the transistors 6a, 6b into conduction to form
a current path between the output terminals out.sub.1,
out.sub.2.
With the above-described connections among the transistors 6a, 6b
and diodes 6c, 6d in the switching element 6, the relay will
operate regardless of the polarity of the load connected across the
output terminals out.sub.1, out.sub.2. In other words, in a case
where the output terminals out.sub.1, out.sub.2 are of positive and
negative polarity, respectively, current will flow through
transistor 6a and diode 6d. If the polarities are reversed, then
current will flow through transistor 6b and diode 6c. Thus, the
relay is of non-polar type as it will operate irrespective of the
load polarity.
When a relay of non-polarized operation is not required, the
switching element 6 need be provided with only one transistor 16a,
as shown in FIG. 2. This will enable the relay to be used with a
load where the polarity of output terminal out.sub.1 will be
positive and that of output terminal out.sub.2 negative. In this
case also a diode, indicated at 16b, will be connected across the
collector and emitter of the transistor to prevent reverse
bias.
FIG. 3 illustrates another embodiment of the present invention
useful for increasing the current-carrying capacity of the
switching element. In this arrangement, the collectors of the
bipolar transistors 6a, 6b are tied together, one terminal of the
load is connected to the common collectors, and the other terminal
of the load is connected to the common emitters. Thus the
arrangement is such that the commonly connected collectors serve as
the output terminal out.sub.1 and the commonly connected emitters
serve as the output terminal out.sub.2.
The reasons for employing the rapidly operable bipolar transistors
in the switching element 6 of the foregoing embodiment are as
follows. In comparison with a switching element using MOSFETs or
the like, the aforementioned bipolar transistors exhibit quicker
on/off action, have a larger current-carrying capacity and are less
costly. A switching element employing these bipolar transistors
consequently is more effective for large-current loads that require
good response.
An arrangement can be adopted wherein the oscillator circuit 1 is
rendered operational for an interval of time during which the
command input IN is high. In other words, the command input IN when
at logical "1" would serve as an enable signal for the oscillator
circuit 1, allowing the AND gate to be deleted from the relay
circuitry.
In accordance with the present invention as described and
illustrated hereinabove, a D.C. command input for controlling the
on/off operation of the contactless relay is temporarily converted
into an A.C. signal. The A.C. signal, upon passage through the
transformer 3, is converted into a D.C. signal by the rectifying
and smoothing circuits 4, 5 to drive a bipolar transistor(s)
serving as a switch. With the contactless relay of the invention,
therefore, the input and output of the relay are isolated D.C.-wise
by the transformer 3. Moreover, the relay is small in size and has
the advantage of a relay with contacts in that its output terminals
are non-polarized. Since the switching element uses bipolar
transistors, the relay, besides being contactless, is endowed with
a comparatively large current carrying capacity and quick response.
In addition, the relay can be constructed at low cost. Owing to the
contactless nature of the relay, semi-permanent operation is
assured. This extends the useful life of the device employing the
relay and facilitates maintenance.
As many apparently widely different embodiments of the present
invention can be made without departing from the spirit and scope
thereof, it is to be understood that the invention is not limited
to the specific embodiments thereof except as defined in the
appended claims.
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